The invention relates to bleach activator particles which have improved solubility and performance in an aqueous wash liquor. The present invention also encompasses detergent compositions utilizing these particles.
It is well known that by adding surface bleaching components to a detergent composition that the detergent composition""s cleaning performance can be improved. Bleaches are useful for removing dingy soils (which is usually a mixture of particulate and oily materials) from the surface of a textile and as well as soil build-up which after numerous cycles of usage and washing results in muted colors and grayer white fabric areas. Bleaches are also very useful in reducing the microbial presence on textiles which provides sanitization benefits increasingly desired by consumers.
Typically, peroxygen bleaches capable of yielding hydrogen peroxide in aqueous solutions are used to treat textile and fabric articles and are very effective for removing stains as well as soil materials from textiles. But such bleaching species are also highly temperature dependent as they are effective only in aqueous solutions or wash liquors having a temperature of greater than about 60xc2x0 C., but becoming less and less effective as the temperature of the solution is lowered below 60xc2x0 C.; while increasing the concentration of the hydrogen peroxide bleaching species extends the useful effective range of the bleaching species below 60xc2x0 C., such increases are not only inpracticable for large-scale commercial detergent production but are also ineffective at lower wash temperatures. This temperature dependence of peroxygen bleaches is significant because such bleaches are commonly used as a detergent adjuvant in textile wash processes that utilize an automatic household washing machine at wash water temperatures below 60xc2x0 C. (particularly in North America and Japan).
A highly effective solution to the low-temperature inefficacy of hydrogen peroxide, is the use of a peroxygen bleach activator that reacts with hydrogen peroxide to form an organic peracid bleaching species. This may occur in situ in a bleaching solution as a result of a perhydrolysis reaction between hydrogen peroxide anions and a bleach activator. Suitable bleach activators are widely disclosed in the consumer laundry detergent art. The bleaching mechanism generally, and the surface bleaching mechanism in particular, in the washing solution are not completely understood. While not intending to be limited by theory, however, it is believed that the bleach activator undergoes nucleophilic attack by a perhydroxide anion, for example from aqueous hydrogen peroxide, to form a percarboxylic acid (the perhydrolysis reaction).
Typically these bleach activators are incorporated into powder or granular detergent products as a particle such as an admixed extrudate or granule. Unfortunately, when they are added as one component of consumer detergent product these peroxygen bleach activators have a tendency to react with other components of the detergent product or the moisture inherently present in the product or ambient moisture in the storage container. This greatly compromises their stability and eventual performance benefits. This instability is exacerbated when the detergent product is stored at higher temperatures. In order to maintain the stability of the activator prior to its use by a consumer it is necessary that the activator-containing particle contain binder materials that not only ensure the physical cohesion of the particle but also inhibit the reaction of the activator with ambient moisture and other detergent components so as to provide stability and permanence to the activator material.
But while this binder material may stabilize the bleach activator, it may also insulate the activator from its use environment that it greatly compromises the rate of dispersion and dissolution of the peroxygen bleach activator in aqueous solution or wash liquor. If bleach activator particles are prevented from dissolving in the wash liquor inside an automatic washing machine then bleaching performance may be nonexistence since there is little or no activator molecules to react with the hydrogen peroxide to form the low-temperature peroxy acid bleaching species. Because dissolution is generally less rapid in cold water, then the bleach activator particles are inhibited from provided their benefits in the very wash environments in which it is most important for them do so.
Accordingly, there is a continuing need for a specially-formulated bleach activator-containing particle which is not only stable during storage in the detergent product box but is also readily soluble in water, particularly relatively water, when added to a wash liquor during an aqueous wash process.
It has now been discovered in the present invention that the use of specific compounds as well as combinations of such compounds in the binder system of a bleach activator particle can maintain the stability and prevent the degradation of the bleach activator without impeding the rapid and ready dissolution of the particle when added to an aqueous solution or wash liquor, particularly when the temperature of the aqueous solution or wash liquor is relatively cold.
The bleach activator particles according to a first aspect of the present invention comprise a bleach activator having the general formula: 
wherein R is an alkyl group containing from about 5 to about 18 carbon atoms wherein the longest linear alkyl chain extending from and including the carbonyl carbon contains from about 6 to about 10 carbon atoms and L is a leaving group, the conjugate acid of which has a pKxcex1 in the range of from about 4 to about 13, preferably from about 6 to about 11, most preferably from about 8 to about 11. In this first aspect, the bleach activator particles also contain a binder material which comprises from about 0.1% to about 15% of an inorganic salt capable of absorbing water of hydration.
In a second aspect of the present invention, the bleach activator particles comprise a bleach activator having the same general activator formula described above as well as a binder material comprising from about 0.1% to about 15% of a saturated fatty acid having the formula: 
wherein Rx is an alkyl group which contains less than 15, preferably less than about 11, more preferably less than about 9 carbon atoms and wherein the particle contains no saturated fatty acids of the above formula wherein Rx contains more than 15 carbon atoms. It is preferred that these fatty acids be used in combination with polyethylene glycols which are discussed in greater detail below.
In additional aspect, the present invention relates to bleach-containing detergent compositions containing the above described bleach activator and characterized by having a residual weight of less than about 4%, preferably less than about 3%, more preferably less than about 1% as measured by the blue pouch test and a bleach activator stability of at least about 50%, preferably at least about 70%, more preferably at least about 90% as measured by the storage stability test.
All parts, percentages and ratios used herein are expressed as percent weight unless otherwise specified. All documents cited are, in relevant part, incorporated herein by reference.